Thin Data Reader Cap

ABSTRACT

A data reader may have a magnetoresistive stack with a magnetically free layer decoupled from a first shield by a cap. The cap can have one or more sub-layers respectively configured with a thickness of 4 nm or less as measured parallel to a longitudinal axis of the magnetoresistive stack on an air bearing surface.

SUMMARY

A data reader, in accordance with various embodiments, is configuredwith a cap that is composed of chemically different layers. A datareader can have a magnetoresistive stack with a magnetically free layerdecoupled from a first shield by a cap. The cap may have cap and masklayers with the cap layer having a thickness of 4 nm or less as measuredparallel to the longitudinal axis of the magnetoresistive stack on anair bearing surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 displays an air bearing view line representation of a portion ofan example data reader arranged in accordance with various embodiments.

FIG. 2 shows an air bearing view line representation of a portion of anexample data reader configured in accordance with some embodiments.

FIG. 3 is an air bearing view line representation of a portion of anexample data reader arranged in accordance with assorted embodiments.

FIG. 4 is a block representation of an example data storage systemconfigured and operated in accordance with some embodiments.

FIGS. 5A & 5B respectively convey an example data reader fabricationroutine carried out in accordance with various embodiments.

DETAILED DESCRIPTION

To advance data capacity, the recording density of data in a datastorage device increases and data reader structures must be reduced insize. However, formation of reduced data reader dimensions can bedifficult due at least to process variability in fabricating thin filmswith nanometer dimensions. Hence, there is a continued goal to provide adata reader with reduced dimensions and less susceptibility tofabrication variability.

To address that goal, a data reader, in some embodiments, has amagnetoresistive stack with a magnetically free layer decoupled from afirst shield by a cap that has a stack cap layer and a first mask layerwith the stack cap layer having a thickness of 4 nm or less as measuredparallel to the longitudinal axis of the magnetoresistive stack on anair bearing surface (ABS). The reduced dimensions of the cap allows themagnetoresistive stack to have a smaller width with less reader widthoffset, which is characterized as the difference between a patternedmask width and a finished sensor reader width. A narrower data readerwidth allows narrower data track dimensions that increases overall datacapacity and optimizes signal strength versus position of a data bit inrelation to the reader's centerline.

While a data reader employing a thin cap can be utilized in an unlimitedvariety of environments and systems, FIG. 1 provides blockrepresentation of a portion of an example data reader 100 that can betuned and employed in a data storage system in accordance with variousembodiments. It is noted that anisotropic magnetoresistive (AMR)sensors, tunneling magnetic resistance (TMR) sensors and giantmagnetoresistance (GMR) sensors can utilize various embodiments of thepresent disclosure. Assorted embodiments are directed tomagnetoresistive sensors based on new physical phenomena, such aslateral spin valve (LSV), spin-hall effect (SHE), and spin torqueoscillation (STO), and may also include devices with configurations suchas multiple stacked sensors. The data reader 100 has a magnetoresistive(MR) stack 102 that can be disposed vertically between magnetic shields,of which a leading shield 104 is shown in FIG. 1. The MR stack 102 canalso be shielded by side shields 106 separated from the stack 102 byinsulating layers 108.

It is noted that the terms “leading” and “trailing” are not limiting andare meant to denote the shields position relative to data bits rotatingon an adjacent data storage medium. It is also noted that the verticaldirection is aligned with the Y axis and can be characterized as adowntrack direction that is perpendicular to the lateral direction thatis aligned with the X axis and can be characterized as a crosstrackdirection.

The MR stack 102 can be an unlimited variety of laminations that candiscern between data bits written on a data storage medium. The freestructure 110 can be one or more magnetic and non-magnetic layers thatare magnetically sensitive to external magnetic bits, despite having adefault magnetization direction that may be set by one or more biasingelements in the data reader 100.

Although not required or limiting, fabrication of at least a cap layer112 portion of the MR stack 102 can position a mask 114 in contact withthe cap layer 112. The cap layer 112 is designed with a thickness 116,as measured parallel to the Y axis and longitudinal axis 118 of thestack 102, that protects a free structure 110 of the MR stack 102 frombeing oxidized and damaged in the sequential manufacture operations.

If the cap thickness 116 is relatively thick, such as 6 nm or more, themask thickness 120 in combination with the cap thickness 116 result inshadowing and/or redeposition effects during formation of the MR readerwidth 122 that produce a reader width offset that is measured as thedifference between the reader width 122 and the mask width 126. Thus, athicker cap layer 112 can result in greater width offset and largerreader width 122.

The reader width offset can increase the size of the reader width 122and inhibit the construction of designed reader 100 dimensions. However,there is a balance between cap thickness 116 and enough cap material toprotect the free structure 110 from damage and instability. For example,thinner cap layer thicknesses 116 can result in degraded strength ofmagnetic biasing field on free layer structure 110, which can cause freelayer instability.

With these issues in mind, a data reader 130 can be configured withmultiple processing layers in accordance with assorted embodiments, asillustrated in the ABS view line representation of FIG. 2. The datareader 130 has a magnetoresistive stack 102 that employs a fixedmagnetization structure 132 that can be one or more magnetic andnon-magnetic layers that retain a fixed magnetization orientation inresponse to encountering a data bit. The fixed magnetization structure132 has a width 134 along a cross-track direction, parallel to the Xaxis, that is greater than the reader width 122, which can increasestability of the data reader 130 despite nanometer scale dimensions. Itis noted that the fixed magnetization structure 132 can be configuredwith any uniform or varying width 134 on the ABS, such as the readerwidth 122.

The fixed magnetization structure 132 is separated from the freestructure 110 by a non-magnetic layer 136 that can be a spacer orbarrier depending on the material selection. To provide a reduced readerwidth 122 with decreased reader width offset, the cap 112 is configuredas a lamination of a cap layer 140 and a first mask layer 142 that actin concert with the second mask layer 114 to protect the free structure110 during fabrication. Hence, the tuning of the material and dimensionsof the cap layer 140 and first mask layer 142 can mitigate reader widthoffset and allow for decreased cap thickness 144 and reader width 122 ina finished reader configuration.

Various embodiments construct the respective cap layer 140 and firstmask layer 142 with materials that prevent magnetoresistive stack 102degradation during processing and are resistant to oxidation, such asplatinum-group based materials like Ir, Ru, and Pt. The cap layer 140and first mask layer 142 can be dissimilar materials and thicknesses 144and 146 with the first cap layer 140 having a larger thickness 144 insome embodiments. Although not limiting, the first mask layer 142 can bea conductive material that is a metal, such as Pt or Ta, an oxide, suchas SiO₂, and a nitride, such as TaN. The first mask layer 142 may bearranged to be an oxide or nitride, such as CuN, at room temperaturethat decomposes at high temperature to ensure conductivity. That is,layers 140 and 142 can be chemically different, which can be selectedduring reactive etching of layer 142.

The material selection of the cap layer 140 and first mask layer 142 canallow different material removal means to be used to pattern oreliminate the respective layers. In other words, the cap layer 140 canbe configured to be inert to reactive etching while the first mask layer142 is inert to the other etching material removal means. It is alsocontemplated that one, or both, of the cap layer 140 and first masklayer 142 can act as a chemical mechanical polish stop.

FIG. 3 displays an ABS view line representation of a portion of anexample data reader 150 arranged in accordance with some embodimentswith a reduced cap thickness 152 and decreased stack width 154. It isnoted that the cap 156 shown in data reader 150 can be a single layer,such as cap layer 140, or a bi-layer lamination of the similar ordissimilar materials, such as Ir, Ru, and Pt. After the second masklayer 114 and whatever portion of the cap layer 140 have been removedand patterned, the magnetoresistive stack 102 is disposed between andcontacting leading 104 and trailing 158 shields. In some embodiments,the trailing shield 158 is characterized as a first shield and theleading shield 104 is characterized as a second shield.

While not required or limiting, one, or both, shields 104 and 158 canhave a fixed magnetization structure 160, which may be a single magneticmaterial or a synthetic antiferromagnet (SAF) lamination of layerspinned by an antiferromagnetic material. As shown, the trailing shield158 has a shield layer 162 contacting the fixed magnetization structure160. The shield layer 162 can be one or more materials and layers thatcan complement the fixed magnetization structure 160 to provideoptimized shielding of stray magnetic flux from the magnetoresistivestack 102.

Although not required, the fixed magnetization structure 160 of thetrailing shield 158 can be coupled to and magnetically stabilize therespective side shields 106.

It is contemplated that at least one seed layer can be positionedbetween the side shields 106 and/or magnetoresistive stack 102 and thetrailing shield 158, which can promote coupling and/or crystallographicformation of the various materials of the fixed magnetization structure160. The fixed magnetization structure 160 can have one or moremagnetizations that can be parallel to the X axis, or canted at anon-normal angle with respect to the X-Y plane and ABS.

The tuned materials, number of layers, and magnetizations of thetrailing shield 158 is physically and magnetically separated from thefree structure 110 by the cap 156. In some embodiments, the thickness152 of the cap 156 is tuned to provide a predetermined bias on the freestructure 110 that stabilizes data reader 150 operation withoutdegrading the free structure's 110 accuracy in sensing encountered databits. It is noted that the magnetoresistive stack 102 in reader 150 hasa generally rectangular shape. This is not required or limiting, as thestack 102 can have canted sidewalls that generally define a trapezoidalshape proximal the free structure 110 as displayed in readers 100 and130.

FIG. 4 displays a block representation of a portion of an example datastorage system 170 in which a tuned data reader can be commissioned inaccordance with some embodiments. Although not required or limiting, thedata storage system 170 can have one or more data storage devices 172that are configured with at least one data storage means. It iscontemplated that various solid-state volatile and non-volatile memoriescan be used as data storage means.

Assorted embodiments arrange at least one data storage device 172 of thedata storage system 170 as a hard disk drive with at least one localcontroller 174 directing operations of a transducing assembly 176 thatconsists of a plurality of data bits 178 stored in various data track180 portions of a data storage medium 182. One or more data bits 178 canbe accessed individually, concurrently, and successively by atransducing head 184 suspended from an actuating assembly 186 to presentdata reader and data writer components. In operation, a spindle 188 canrotate the data storage medium 182 to produce an air bearing 190 onwhich the head 184 flies, as directed by the controller 174.

While the data storage device 172 can operate solely with the localcontroller 174, various embodiments connect the data storage device 172with at least one remote host 192 via a wired and/or wireless network194. The remote connection of the data storage device 172 allows theremote host 192 to provide additional processing, data storage, andsecurity capabilities without impinging on the operation of the datastorage device 172. It is contemplated that the data storage system 170can incorporated any number of data readers that are arranged to provideoptimized side shield data reader biasing and shielding structures.

Although not required or limiting, FIGS. 5A & 5B convey an example datareader fabrication routine 200 carried out in accordance with variousembodiments to construct a data reader tuned to a predetermined datastorage environment. The routine 200 begins by depositing a leadingshield onto a substrate followed by a fixed magnetization structureportion of a magnetoresistive stack in step 202. Example reader 250 ofFIG. 5B illustrates a portion of a leading shield 252 and a fixedmagnetization structure 254 that can be respectively tuned forthickness, material, number of layers, and magnetic characteristics,such as magnetic moment and uniaxial anisotropy, without limitation.

Next, step 204 successively forms a non-magnetic layer 262, magneticallyfree layer 264, cap layer 266, and first mask layer 268 onto the stackfixed magnetization structure, as shown in reader 260 of FIG. 5B. Thevarious layers created in step 204 can be different materials andthicknesses to ensure protection and magnetic operation of themagnetically free structure. A second mask layer 270 is then depositedin step 206 atop the first mask layer to allow step 208 to patternportions of the first and second mask layers. Reader 280 depicts howremoving less than all the material of each layer can respectively shapethe second 270 and first 268 mask layers.

Step 210 proceeds to form side shields on lateral sides of themagnetoresistive stack. It is noted that step 210 can remove portions ofthe non-magnetic layer, free layer and cap layer, to provide arectangular, curvilinear, or trapezoidal shape for a portion of themagnetoresistive stack. As shown in reader 290 of FIG. 5B, the formationof the side shields can involve the deposition of one or morenon-magnetic gap layers 292 that separate the side shields 294 from thefree structure 264, fixed magnetization structure 254, cap layer 266,and first mask layer 268.

Routine 200 advances to step 212 where the second mask layer is removedto produce the planar top stack surface 302 illustrated by reader 300.Various embodiments utilize different material removal means, such asreactive etching and polishing, that ensure the cap layer remains intactand protecting the stack free layer. That is, material removal processescan be selectively utilized to remove one layer at a time withoutremoving any portions of the cap layer that protects the magneticallyfree layer of the stack. With the planar reader surface 302 beingprepared, step 214 deposits a fixed magnetization structure that acts aspart of a trailing shield. The fixed magnetization structure can be anynumber of materials and layers that are coupled to the side shieldswithout being coupled to the stack free layer. Reader 310 of FIG. 5Bdisplays how a fixed magnetization structure 312 contacts the cap layer266 and respective side shields 294. It is noted that some embodimentsconfigure the steps 212 and 214 to remove less than all the first masklayer so that a bi-layer cap is present between the shield fixedmagnetization structure and the magnetically free layer with the firstmask layer having a smaller thickness than the cap layer.

Finally, at least one shield layer is deposited on the shield fixedmagnetization structure to complete the data reader, as shown by layer314 in reader 310. It is noted that the various steps of routine 200 andrepresentative illustrations of FIG. 5B are merely exemplary and are notrequired. As such, any step can be modified or removed just as any stepor decision can be inserted without limitation. For example, at leastone additional step can incorporate the completed data reader into atransducing head while another step may utilize the data reader to sensedata bits in a hard disk drive data storage environment.

Through the various data reader cap embodiments, a magnetoresistivestack can be fabricated with smaller dimensions while the magneticallyfree layer of the stack remains protected. The utilization of a masksub-layer can act in concert with a mask to allow for a thinner caplayer and reduced reader offset. The ability to tune the cap formaterials and numbers of layers allows data reader fabrication tominimize shadowing and redeposition effects that increase the width ofthe reader on the ABS and decrease the possible data track resolution ona data storage device.

It is to be understood that even though numerous characteristics ofvarious embodiments of the present disclosure have been set forth in theforegoing description, together with details of the structure andfunction of various embodiments, this detailed description isillustrative only, and changes may be made in detail, especially inmatters of structure and arrangements of parts within the principles ofthe present technology to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed. Forexample, the particular elements may vary depending on the particularapplication without departing from the spirit and scope of the presentdisclosure.

1. An apparatus comprising a magnetoresistive stack having a less than 4nm reader width offset and comprising a magnetically free layercontacting a bi-layer cap comprising a cap layer and a first mask layer,the cap layer deposited with having a width equal to or greater thanthat of the first mask layer as measured perpendicular to a longitudinalaxis of the magnetoresistive stack and with a thickness of 4 nm or lessas measured parallel to the longitudinal axis of the magnetoresistivestack on an air bearing surface (ABS), the cap layer having a thicknessof 2 nm or more, decoupling the magnetically free layer from a firstshield, and contacting the magnetically free layer and the first shieldafter the first mask layer is removed.
 2. The apparatus of claim 1,wherein the first mask layer has a vertical sidewall oriented parallelto the longitudinal axis of the magnetoresistive stack.
 3. The apparatusof claim 1, wherein the cap and first mask layers are differentmaterials.
 4. The apparatus of claim 3, wherein the cap layer comprisesa first polish stop material and the first mask layer comprises a secondmaterial which can be removed by reactive etch.
 5. The apparatus ofclaim 1, wherein the magnetoresistive stack comprises a fixedmagnetization structure having a greater width than the free layer. 6.The apparatus of claim 1, wherein the magnetoresistive stack contactsfirst and second shields along the longitudinal axis, themagnetoresistive stack disposed between and separated from first andsecond side shields along a transverse axis oriented perpendicular tothe longitudinal axis.
 7. The apparatus of claim 1, wherein a secondmask layer contacts the first mask layer prior to removal of the firstmask layer, the second mask layer selected to be removed by a techniquethat will not remove the first mask layer.
 8. The apparatus of claim 1,wherein the first mask layer comprises a metal, oxide, nitride material,or amorphous Carbon.
 9. An apparatus comprising a magnetoresistive stackhaving a less than 4 nm reader width offset and comprising amagnetically free layer decoupled from a shield by a cap having athickness of 2 nm or less as measured parallel to a longitudinal axis ofthe magnetoresistive stack on an air bearing surface (ABS) after a firstmask layer is removed, the cap comprising a material that decomposesinto metal, the cap disposed between and contacting the magneticallyfree layer and the shield.
 10. The apparatus of claim 9, wherein the capcomprises CuN.
 11. The apparatus of claim 9, wherein the cap decomposesfrom an oxide or nitride to a metal.
 12. The apparatus of claim 9,wherein the shield comprises a fixed magnetization structure.
 13. Amethod comprising: depositing a magnetoresistive stack having amagnetically free layer; forming a cap layer atop the magnetically freelayer, the cap having a thickness of 4 nm or less as measured parallelto a longitudinal axis of the magnetoresistive stack on an air bearingsurface (ABS); depositing a first mask layer on the cap layer; forming asecond mask layer on the first mask layer, the first and second layersbeing independently definable; patterning the first and second masklayers to a common reduced width; patterning the magnetoresistive stackto have a less than 4 nm reader width offset; depositing an isolationstructure and side shield structure; removing the second mask layer;removing the first mask layer to provide a cap thickness of 2 nm ormore; and depositing a shield in contact with the cap layer, the caplayer decoupling the magnetically free layer from the shield.
 14. Themethod of claim 13, wherein the first mask layer is removed with adifferent material removal process than the second mask layer.
 15. Themethod of claim 14, wherein the second mask layer is removed with areactive etch material removal process, the first mask layer being inertto the reactive etch material removal process.
 16. The method of claim15, wherein the first mask layer is patterned with a process that doesnot add to the reader width offset.
 17. The method of claim 13, whereinthe first mask layer protects the cap and magnetically free layer duringat least one subsequent process prior to deposition of the shield. 18.The method of claim 17, wherein the first mask layer is removedimmediately prior to shield deposition.
 19. The method of claim 15,wherein the reactive etch material removal process comprises aninductively coupled plasma.
 20. The method of claim 13, wherein thefirst mask layer masks the cap layer from a material removal processthat removes the second mask layer.